A multi-scale near-surface tomographic velocity modeling method and modeling system

Abstract

The invention discloses a multi-scale near-surface tomographic velocity modeling method and a modeling system, comprising: step 1: inputting first-arrival travel time and initial velocity model; step 2: calculating theoretical travel time and ray path based on the initial velocity model; Step 3: Obtain the speed modifier, and according to the speed modifier, modify the initial speed model to obtain the current speed model; Step 4: Compare the speed modifier with the preset speed modifier threshold; Step 5: If the speed modifier is greater than or equal to the preset speed To modify the threshold value, compare the maximum offset with the offset threshold; Step 6: If the maximum offset is greater than or equal to the offset threshold, use the current velocity model as the final velocity model. The multi-scale near-surface tomographic velocity modeling method of the present invention improves the inversion accuracy by inputting the first-arrival travel time and the initial velocity model, and modifying the initial velocity model according to the velocity modification value, and can establish a high-precision near-surface velocity model.

Description

technical field [0001] The invention belongs to the field of oil and gas exploration, and in particular relates to a multi-scale near-surface tomographic velocity modeling method and a modeling system. Background technique [0002] With the advancement of seismic exploration to double-complex areas, the surface elevation, near-surface velocity, and thickness change drastically, which brings great challenges to high-precision seismic imaging. In order to improve the imaging accuracy of subsurface structures, building a more refined near-surface velocity model is one of the key technologies. The tomographic velocity modeling of near-surface first-arrival traveltime is a common method for near-surface modeling. In this method, by picking up the travel time of the first arrival wave, the model modification amount is obtained according to the theoretical travel time of the initial model and the residual of the picked travel time, and the velocity model is continuously updated an...

AI Technical Summary

Problems solved by technology

This type of method is flexible to solve, but due to the ill-conditioned nature of the ray tomography matrix, the matrix solution is unstable, which affects the inversion accuracy; the second type is to average the travel time residuals on the ray path through the back projection method. The representative is the SIRT method

The inversion results of this type of method are stable, but the disadvantage is low resolution; the third type of method is the adjoint state method, which does not require ray tracing, and the velocity modification value can be obtained through two calculations of forward modeling

This method saves the traditional ray tracing process, but the physical meaning is not clear, and the establishment of the Hessian matrix is ​​difficult, and the ability to improve accuracy is limited

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